Immunocytochemical localization of endopeptidase-24.11 in the nucleus tractus solitarius of the rat brain.
Recently, it has been hypothesized that the N-terminal portion of substance P (SP), SP(1-7), which results from the action of endopeptidase 24.11 (EC3.4.24.11), could be involved in mediating the depressor effects of baroreceptor afferent activation via its action on cells in the nucleus tractus solitarius (NTS). In this study, the binding of a monoclonal antibody to endopeptidase 24.11 was examined immunohistochemically at the level of the caudal medulla of the rat brain. By light microscopy, intense immunoreactivity was seen in the NTS, in fibers bordering the area postrema, and in the area postrema itself. After electron microscopy, endopeptidase 24.11-like immunoreactivity was seen to be associated with the cytoskeleton and plasma membrane in axons, dendrites and glial processes. Antigen was also associated with synaptic vesicles and plasma membranes in presynaptic terminals forming mainly axo-dendritic synapses typical of vagal afferent terminals involved in the baroreceptor reflex. Thus, endopeptidase 24.11 appears to be localized at sites where it could effectively process SP prior to its binding to postsynaptic receptors.
Lasher
R S
RS
Department of Cellular and Structural Biology, University of Colorado Medical School, Denver 80262.
Lutz
E M
EM
Mulholland
F
F
Sanderson
R
R
Stewart
J M
JM
Bublitz
C
C
D000595:Amino Acid Sequence; D000818:Animals; D007124:Immunoenzyme Techniques; D008526:Medulla Oblongata / Q000201:enzymology* / Q000648:ultrastructure; D008969:Molecular Sequence Data; D015260:Neprilysin / Q000032:analysis*; D015388:Organelles / Q000201:enzymology / Q000648:ultrastructure; D051381:Rats
D015260:Neprilysin